A typical data storage system includes storage control circuitry (e.g., a front-end server, a storage processor, a set of directors, etc.) and hard disk drives. The storage control circuitry performs a variety of data storage operations (e.g., load and store operations) on behalf of one or more external clients by sending hard drive commands to the hard disk drives. A typical command uses an LBA (Logical Block Address) addressing mode in which the command specifies a starting LBA and a count.
A typical hard disk drive includes multiple hard disk platters mounted to a common spindle. Each hard disk platter defines a top surface and a bottom surface for storing data in a non-volatile manner. The hard disk drive further includes a disk drive controller and, for each platter surface, a read head and a write head which are controlled by the disk drive controller to respectively read data from and write data to that platter surface.
In addition to the disk drives that regularly maintain data, it is common practice for a data storage system to include a hot spare disk drive. When a regular disk drive fails, the hot spare disk drive kicks in by taking over the role of the failing disk drive. That is, the storage control circuitry stores a copy of the data that currently exists on the failing disk drive onto the hot spare disk drive. The storage control circuitry then operates the hot spare disk drive in place of the failing disk drive. Typically, the failing disk drive is then removed from the data storage system and discarded by a technician.